The present invention relates to a method for producing pyridine bases by reacting in a gas-phase an aliphatic aldehyde, aliphatic ketone or mixture thereof with ammonia in the presence of a catalyst.
A method for producing pyridine bases by reacting in a gas-phase an aliphatic aldehyde, aliphatic ketone or mixture thereof with ammonia in the presence of a catalyst is known. Various methods are reported, for example, a method in which an amorphous silica-alumina is used as a catalysts, a method in which zeolites such as aluminosilicate and the like are used, as well as other methods. Among the catalysts, zeolite is suitable as a catalyst for producing pyridine bases in which a gas-phase reaction is conducted under high temperature condition, due to its excellent heat-resistance.
As the zeolite used as a catalyst for producing pyridine bases, for example, heteosilicate such as ferrosilicate, borosilicate and gallosilicate, in addition to aluminosilicate, are known. These zeolites are used singly as a catalyst. Alternatively, they are allowed to contain an ion and/or compound of various elements, such as copper, zinc, cadmium, bismuth, chromium, molybdenum, tungsten, cobalt, nickel, ruthenium, rhodium, palladium, iridium and the like, to give a catalyst to be used.
In the production of pyridine bases, it is known that main products, the pyridine bases, are determined by combination of the raw materials, an aliphatic aldehyde and an aliphatic ketone. Typical examples of them are shown in Table 1.
TABLE 1 Raw materials (Aliphatic aldehyde, Main Product Aliphatic ketone) (Pyridine bases) Acetaldehyde .alpha.-picoline + .gamma.-picoline Acetaldehyde + formaldehyde Pyridine + .beta.-picoline Acrolein .beta.-picoline Acrolein + acetaldehyde Pyridine Acrolein + propionaldehyde .beta.-picoline Propionaldehyde + formaldehyde 3,5-lutidine Crotonaldehyde + propionaldehyde 3,4-lutidine Crotonaldehyde + acetone 2,4-lutidine Formaldehyde + acetone 2,6-lutidine Acetone 2,4,6-collidine Methacrolein + methyl ethyl ketone 3,5-lutidine + 2,3,5-collidine
As described above, various pyridine bases can be produced by reacting in a gas-phase an aliphatic aldehyde, aliphatic ketone or mixture thereof with ammonia in the presence of a zeolite as a catalyst. However, the yields of pyridine bases produced by conventional methods are yet low.
For example, in the comparative examples described below, which were conducted by the present inventors and in which acetaldehyde is reacted with ammonia to produce .alpha.-picoline and .gamma.-picoline according to the above-described conventional methods, namely, by using aluminosilicate, ferrosilicate or the like as the catalyst, the yields of .alpha.-picoline and .gamma.-picoline were, respectively, 17.6% and 18.5% when aluminosilicate was used, 18.6% and 17.5% when ferrosilicate was used, and 17.3% and 19.3% when gallosilicate was used.
Thus, the yields of the intended pyridine bases in conventional methods are not yet satisfactory, and further improvement in the yield is desired.
The present inventors have intensively studied for finding a method that can produce pyridine bases in higher yield. As a result, the present inventors have found that, when pyridine bases are produced by reacting in a gas-phase an aliphatic aldehyde, aliphatic ketone or mixture thereof with ammonia in the presence of a zeolite containing titanium and/or cobalt and silicon as zeolite constituent elements in which the atomic ratio of silicon to titanium and/or cobalt is about 5 to about 1000, pyridine bases can be produced at higher yield as compared with the conventional case in which a zeolite such as aluminosilicate, ferrosilicate or the like is used as the catalyst. Thus, the present invention has been completed.